Magnetic resonance imaging techniques provide the opportunity to visualize internal organs at microscopic resolution in live animals and to study the effects of environmentally important chemical agents on perturbations in tissues and organs. Advanced techniques continue to be developed by Dr. G. Allan Johnson of Duke University permitting tissue resolution less than 50 microns in live animals and resolution less than 20 microns in fixed pathology specimens. Recent efforts have focused on obtaining MR images of fixed pathology specimens in which tissue damage is present. The MR images provide an alternative type of 'special stain' in that the proton images show structural details not present in conventionally stained sections. In addition, three-dimensional study and quantitation of findings is facilitated in acquired MR images of these tissue specimens. Current efforts involve implantation of rf coils on the liver surface of rats and collection of multiple high resolution images before. during and after treatment with known hepatotoxic agents. These studies show great promise as a means of monitoring dynamic tissue changes in live animals following exposure to potentially toxic environmental agents.